Prof Andrew M. Blamire

Magnetic resonance imaging (MRI) can detect structural abnormalities in the brain resulting from disease, injury or ageing. Changes observed on clinical MR scans often reflect the final stage of these processes, at a time when irreversible loss of brain tissue has occurred.

MRI shows the distribution of water within the tissue by detecting the magnetic resonance signal from the nucleus of the the hydrogen atoms in each water molecule (the H's in H2O). The technique of proton magnetic resonance spectroscopy (MRS) is similar to MRI but aims to detect signals from hydrogen atoms attached to other important metabolites within brain. Changes in the levels of these metabolites are expected to occur much earlier in the disease process and so may allow us to detect acute damage at a time when we can intervene and salvage brain tissue.

Unlike MRI, the technique of MRS does not generally produce images, instead creating spectra (see figure). Each peak in the spectrum arises from different brain metabolite (NAA, N-acetylaspartate; Cre, Creatine; Cho, Choline; myoI, myo-Inositol; Lac, lactate; Glx, Glutamate and Glutamine; GABA, gamma amino butyric acid). The height of each peak is an indication of metabolite concentrations. The NAA peak arises from the neurons in the brain. Loss of this metabolite indicates damage or loss of neurons.